Variation in individual temperature preferences, not behavioural fever, affects susceptibility to chytridiomycosis in amphibians

Abstract

The ability of wildlife populations to mount rapid responses to novel pathogens will be critical for mitigating the impacts of disease outbreaks in a changing climate. Field studies have documented that amphibians preferring warmer temperatures are less likely to be infected with the fungal pathogen (). However, it is unclear whether this phenomenon is driven by behavioural fever or natural variation in thermal preference. Here, we placed frogs in thermal gradients, tested for temperature preferences and measured growth, prevalence, and the survival of infected animals. Although there was significant individual- and species-level variation in temperature preferences, we found no consistent evidence of behavioural fever across five frog species. Interestingly, for species that preferred warmer temperatures, the preferred temperatures of individuals were negatively correlated with growth on hosts, while the opposite correlation was true for species preferring cooler temperatures. Our results suggest that variation in thermal preference, but not behavioural fever, might shape the outcomes of infections for individuals and populations, potentially resulting in selection for individual hosts and host species whose temperature preferences minimize growth and enhance host survival during epidemics.

Symbiotic endolithic microbes alter host morphology and reduce host vulnerability to high environmental temperatures

“…, Sauer et al. ). Our goal is to find a symbiont–host interaction outcome that is consistent across locations and scales and to evaluate the underlying mechanisms.…”

“…Conversely, environmental extremes can ameliorate parasitic effects to such an extent that decreased infection prevalence can be related to time spent at environmental extremes, that is, areas of potential refuge from infection by parasites. For example, amphibians that spend time above the thermal breadth of growth for chytrid fungus are less likely to be infected (Richards-Zawacki 2010, Nowakowski et al 2016, Sauer et al 2018). Our goal is to find a symbiont-host interaction outcome that is consistent across locations and scales and to evaluate the underlying mechanisms.…”

Effects of latitudinal, seasonal, and daily temperature variations on chytrid fungal infections in a North American frog

“…For example, fever, an elevation in core body temperature, is thought to enhance immunological responses by increasing the cytotoxic activity of neutrophils and macrophages, activating heat shock transcription factors, optimizing cytokine expression, and stimulating T-cell proliferation (Rollins-Smith and Woodhams 2012). However, while heat has been demonstrated to eliminate Bd infections (Chatfield and Richards-Zawacki 2011) and field studies have found patterns consistent with a behavioral fever response to Bd infection (Richards-Zawacki 2010, Rowley and Alford 2013), the occurrence of behavioral fever in response to Batrachochytrium infection has not been demonstrated empirically (Sauer et al 2018). However, while heat has been demonstrated to eliminate Bd infections (Chatfield and Richards-Zawacki 2011) and field studies have found patterns consistent with a behavioral fever response to Bd infection (Richards-Zawacki 2010, Rowley and Alford 2013), the occurrence of behavioral fever in response to Batrachochytrium infection has not been demonstrated empirically (Sauer et al 2018).…”

Effects of historic and projected climate change on the range and impacts of an emerging wildlife disease

“…Therefore, any compensatory changes in common frog behavior to future climate change may be negligible. Whether thermoregulatory behavior serves as an amphibian strategy for managing infections remains to be elucidated (Sauer et al, 2018) but shading has been proposed as an environmental feature that might have negatively impacted the ability of newts to clear chytrid infections because it limited the availability of warm-water patches (Raffel et al, 2010). Thermoregulatory behavior leading to an increase in body temperature above normal range ("behavioral fever") is known to be important for disease mitigation in a range of ectotherms (Boltaña et al, 2013;Elliot, Blanford, & Thomas, 2002;Monagas & Gatten, 1983).…”